Before You Refactor: 7 Essential Considerations for Successful Code Improvements

Greetings, Friends,

Welcome to the 140th issue of The Polymathic Engineer newsletter.

At some point in their careers, every programmer encounters code that induces a sense of dread. It might be a monolithic function lacking comments or a class that deviates entirely from its intended purpose. Your initial impulse might be to discard it all and start afresh with something pristine and elegant, but this isn't always the optimal strategy.

The desire to enhance code is natural and often justified. Effective refactoring makes code more maintainable, easier to comprehend, and less prone to bugs. Conversely, poorly planned refactoring can consume weeks, introduce new defects, and ultimately leave you with a codebase worse than your starting point.

The distinction between successful and failed refactoring often hinges on preparation and approach. This article explores key considerations that can significantly reduce time and frustration for you and your team.

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1. Understand What You're Working With

Before initiating any changes, dedicate time to thoroughly familiarize yourself with the current codebase and its associated tests. Begin by meticulously reading the code to grasp its functionality and the rationale behind its original design.

Every piece of code possesses a history, and comprehending that narrative empowers you to make superior decisions regarding what to preserve, what to modify, and what to discard.

Identify the strengths within the existing system that you wish to retain. Perhaps the error handling mechanism is exceptionally robust, or there's a clever optimization that significantly boosts performance. The presence of areas for improvement doesn't necessitate a complete overhaul.

Pay close attention to the existing tests. What scenarios do they cover? What edge cases do they explore? Tests can reveal crucial requirements and business logic that aren't immediately apparent from the main codebase alone.

This investigative phase is vital for avoiding one of the most common refactoring pitfalls: inadvertently discarding valuable knowledge due to a failure to recognize its importance.

While it's common to believe we can write superior code, we often end up with something no better, or even worse, than the original. Investing time to understand your starting point is the most effective way to ensure your refactored code truly represents an improvement.

2. Resist the Temptation to Rewrite Everything

When confronted with tangled code, the urge to rewrite it entirely is powerful, yet this approach is rarely the optimal solution.

Even if the current code appears inelegant, it is functional, has undergone testing, review, and extensive use in production. It incorporates workarounds for edge cases you haven't considered and fixes for bugs that took considerable time to discover and resolve.

When you jettison existing code, you also discard all the accumulated information and lessons learned. The new code you write might reintroduce the same obscure bugs that were already fixed in the older version, forcing you to spend weeks rediscovering problems that have long been solved.

This isn't to say that you should never replace substantial sections of code, but ensure you have a compelling justification beyond mere sentiments like "I believe I can do it better" or "This code is difficult to read."

3. Make Changes Incrementally

Modifying hundreds of lines of code simultaneously makes it exceedingly difficult to ascertain the impact on the system. Small, incremental changes are far more manageable and significantly less risky.

Incremental changes facilitate rapid feedback through tests and real-world usage. If an issue arises, pinpointing the cause becomes much simpler when only a small segment of code has been altered.

No one desires to see a multitude of failed tests after implementing a change. Such scenarios lead to frustration and pressure, often resulting in poor decisions and rushed fixes. A few test failures at a time are far more manageable.

My preferred strategy involves making the smallest possible change that propels you in the correct direction, then verifying that everything remains functional. Run the tests. Confirm the system behaves as expected. Only after you are confident in the efficacy of the change should you proceed to the next improvement. This approach demands patience but fosters confidence.

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4. Preserve and Build Upon Existing Tests

Tests represent one of your most valuable assets during refactoring. They alert you when something has been broken, providing confidence that your changes are correct. However, many developers mistakenly discard existing tests too hastily.

Tests serve as living documentation of how the production code is expected to behave. When you discard tests without understanding them, you are effectively throwing away that invaluable documentation.

Before deleting any test, endeavor to comprehend its original purpose. Even if some tests may not appear relevant to your new design, they frequently capture edge cases or business requirements that are not immediately obvious from the code alone.

As you modify code, ensure that existing tests continue to pass. If a test fails, do not immediately assume the test is incorrect. Instead, strive to understand what the test was safeguarding against and whether your new code correctly handles that specific case.

If you find it necessary to modify tests to accommodate your new code, proceed with caution. Ensure you are still validating the same behavior, albeit in a different manner. Should you decide a test is no longer needed, document your reasoning. Make a note or create a ticket clarifying what the test verified and why it has become redundant.

5. Check Your Motivations

Before embarking on any refactoring project, introspectively question your underlying motivations for making these changes.

"The code doesn't align with my personal style" is an insufficient reason for refactoring. Similarly, "I believe I could implement this more effectively than the previous programmer" is driven by ego, not by genuine improvements to the existing system.

Code merely looking different from your preferred style does not inherently mean it requires modification. Every change introduces risk, and that risk must be carefully weighed against tangible benefits.

Valid reasons for refactoring include: the code is difficult to understand and modify, it contains known bugs that are challenging to fix within its current structure, or it significantly impedes performance.

Effective refactoring objectively enhances the system. If you cannot identify specific, measurable improvements, you should reconsider the necessity of the refactoring.

6. Evaluate Technology Changes Carefully

One of the least justifiable reasons for refactoring is the desire to utilize the latest and greatest technology. Thoughts such as "This code is so outdated" or "We could achieve this much better with the new framework" are alluring, but they are rarely sufficient to warrant a major refactoring effort. New technology often feels exciting but also carries inherent risks.

Before undertaking a complete rewrite in a new language or framework, meticulously weigh the pros and cons. Will the new technology genuinely lead to improved functionality, easier maintenance, or enhanced productivity? Or does it simply appear more contemporary?

Occasionally, technological shifts are imperative. You might be using unsupported software or components with significant security vulnerabilities. However, ensure that your decisions are grounded in real business necessities, not merely a desire to work with something more novel.

7. Accept That Refactoring Can Fail

An uncomfortable truth is that refactoring does not always result in improvements.

Sometimes, despite your best intentions and meticulous planning, you end up with code no better than your starting point. On occasion, it can even be worse. Over the years, I've witnessed several failed refactoring attempts. Teams spent months rewriting functional systems, only to produce code that was harder to maintain, more buggy, or less performant than the original. It's an unfortunate reality, but it's part of the human element in software development.

This does not imply that you should abstain from refactoring. Rather, it underscores the importance of being realistic about the risks and having a contingency plan for when things deviate from expectations.

Be prepared to halt the refactoring process if it's not yielding the anticipated results. Sometimes, the most prudent decision is to abandon a refactoring project and revert to the existing code, even if it's imperfect.

Interesting Reading

• To Cache or Not to Cache by Raul Junco
• Most Important Tips for System Design Interviews by Saurabh Dashora
• Why I Can't Stop Digging by Riccardo Causo

The Polymathic Engineer is a reader-supported publication. To receive new posts and support my work, consider becoming a free or paid subscriber.